These ongoing studies continued to test the working hypothesis that growth hormone-induced increases in insulin-like growth factor-I (IGF-I) regulates the tempo of puberty and promotes fertility in adult females. IGF-I for administration was generously provided by Genentech Inc. and the somatostatin analogue, Octreotide, was generously provided by Sandoz Pharmaceuticals. Major findings include 1) IGF-I administration accelerates the tempo of puberty in female monkeys, advancing the age at 1st ovulation; 2) IGF-I administration enhanced the pituitary response in luteinizing hormone (LH) secretion to the excitatory amino acid analog, NMDA in post menarchial females; 3) neither IGF-I supplementation nor treatment with a somatostatin analogue (which lowers endogenous IGF-I) affected parameters of ovulatory cycles in adult females; 4) neither IGF-I supplementation nor treatment with a somatostatin analogue affected the pituitary response in LH secretion to an LH re leasing hormone analog in post-pubertal or adult females; 5) IGF-I increases serum concentrations of IGFBP-3, effectively increasing its bioactivity by slowing degradation. These data indicate that peripheral increases in IGF-I and IGFBP-3 play an important role regulating puberty in females but is not involved in the maintenance of fertility in adults. FUNDING NIH / NICHD $87,692 4/01/82 - 11/30/98 PUBLICATIONS Wilson, M.E. Regulation of the growth hormone - insulin-like growth factor-I (IGF-I) axis in developing and adult monkeys is affected by estradiol replacement and supplementation with IGF-I. J. of Clin. Endocrinol. Metab. 83:2018-2028, 1998. Wilson, M.E. Premature elevation in insulin-like growth factor-I advances first ovulation in rhesus monkeys. J. Endocrinol. 158:247-257, 1998. Wilson, M.E. Effects of estradiol and exogenous insulin-like growth factor (IGF) -I on the IGF-I axis during GH inhibition and antagonism J. of Clin. Endocrinol. Metab. 83:4013-4021, 1998. Wilson, M.E. Continuous subcutaneous infusion rather than twice daily injections of insulin-like growth (IGF) -I more effectively elevates serum IGF binding (IGFBP) -3 in female monkeys. Eur. J. Endocrinol. (In press). Wilson, M.E. and Lackey, S. IGF-I but not the IGF-I variant Long R3 IGF-I increases serum IGFBP-3 in adolescent monkeys. Growth Hormone & IGF Res. (In press). P51 RR00165-38 1/1/98 - 12/31/98 Yerkes Regional Primate Research Center